The present invention is related to a system for determining the eccentric characteristics of a tube, and more particularly, to a system for measurement of the wall thickness of the tube by ultrasonic devices for accurately determining the physical characteristics of the tube as related to eccentricity.
When tubes are extruded or drawn, the wall thickness varies, and sometimes these variations propogate throughout the extruding or drawing process so as to result in excessive eccentricity, and thus, in a tubing product of an unacceptable quality. Therefore, it has been found desirable to determine when such eccentricity exceeds certain limits to enable correction of the process or to terminate any further production of a defective tube, before further manufacturing costs are incurred. Moreover, it is necessary to be absolutely certain that measurements used in determining the eccentricity are accurate and reliable such that unnecessary waste does not occur.
Various types of devices have been previously employed to locate defects in or measure the eccentricity of a tube, but for one reason or another such devices have not been entirely satisfactory. For example, certain devices have not been capable of on-line operation, that is, are not capable of eccentricity determination as the tube is extruded, drawn and/or otherwise produced. In other devices used in on-line operations, the structural arrangement and/or manner of operation impose limitations on the production of the tubing.
Therefore, it has become extremely desirable to provide an on-line system for determining eccentricity which can very accurately and reliably determine the maximum deviation in the wall thickness of a tube at any point around its circumference as the tube is extruded, and thus, be used effectively to reduce manufacturing costs and maintain high quality standards, without requiring undesirable changes in the manufacturing process in order to achieve this goal.